X-ray installation



Marh 2! A. BOUWERS X-RAY INSTALLATION Filed Feb. 25. 1928 f I @Ml/w ,Wh/M

Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE ALBERT BOUWERS, OF EINDHOVEN, NETHERLANDS, ASSIGNOR TO N. V. PHILIPS GLOEILAMPENFABR-IEKEN, OF EINDHOVEN, NETHERLANDS, A LMITED LIABILITY COMPANY X-RAY INSTALLATION Application filed February 25, 1928, Serial No. 257,044, and in the Netherlands March 26, 1927.

The invention relates to an X-ray installation for making X-ray photographs with short exposures. In short exposure photography it is necessary to pass a heavy current for a very short time through the X-ray tube in order to obtain good results. An X-ray installation in which only a transformer is used for the supply of the required voltage, cannot comply with this requirement.

An object of the invention is to provide an improved X-ray installation for making short X-ray exposures. Another object of the invention is to provide an installation in which a great storage of energy is available to be absorbed in an X-ray tube Within a very short time.

Other objects will appear from the following description.

In making short X-ray exposures for which a heavy current must be passed for a short time through the tube, it is known to derive this current from a condenser, which owing to the rise of the temperature of the filament, is suddenly discharged across the X-ray tube. In that case, however, serious difficulties are encountered due to the heat inertia of the filament, and when an X-ray photograph is made with inertia it is impossible to produce a satisfactory photograph with a very short exposure. It is therefore essential that short exposure X-ray photographs should be made without inertia.

According to the invention in an X-ray installation for making short X-ray exposures comprising a storage condenser, means are provided causing an abrupt excitation of the discharge of this condenser across an X-ray tube.

One arrangement that is specially adapted for the above purpose also forms an object of the present invention. lt comprises a spark gap which is connected in series with an X-ray tube. A condenser charged up by suitable means is connected so as to supply high tension current to the tube via the spark gap, the latter breaking down at a definite voltage. Another arrangement which lends itself for carrying this invention into effect, is described in my copending application #384,400 filed August 8th, 1929,

and a division of this application and describes particularly means that are provided for alternatively impressing on an auxiliary electrode between the cathode and the anticathode of an X-ray tube, a low potential that prevents the passage of current across the tube and a. higher potential allowing the discharge of the condenser.

In order to control the current passed through the X-ray tube and to prevent too drawing which represents by way of example one embodiment of the invention.

In this drawing, the primary side and the secondary side of a transformer are indicated by 1 and 2 respectively, the latter being connected to the anode of a rectifying valve 4 the cathode of which is connected to one of the terminals of a condenser 5, the other terminal being connected to ground. Preferably the X-ray tube has an outer wall comprising a metal portion 9, said tube being preferably provided with a movable anti-cathode (according to specification Serial N o. 186,522, led April 5, 1927 not shown). Numeral 8 represents the incandescent cathode of the X-ray tube, said incandescent cathode being arranged inside a device 10 for directing the cathode rays on a limited portion of the anticathode mirror, the socalled focussing device. The installation according to the figure is provided with a spark gap 6. Its operation is as follows: When the transformer is connected to a suitable source of A. C. via regulating resistance 3, condenser 5 will gradually be charged via the rectifier 4. As long` as the voltage of the condenser is not suiiiciently high to initiate the spark discharge, no current Will flow through the X-ray tube nothwithstanding that the filament is at a suitable emitting temperature the heating current being closed. At a definite Voltage of the condenser, however, the spark gap 6 breaks down and becomes conductiveand a current will pass through the X-ray tube, the duration and the value of this current being determined by the capacity of the condenser and' by the temperature of the filament. This passage of current lasts, for example, 0.05 sec. and the current intensity will be, for example, 500 milliamperes when the capacity of the condenser is 0.25 mi. and the high tension is 100,000 Volts.

lVhat I claim is:

1. An X-ray installation `for making short X-ray exposures, comprising a storage condenser, means for charging said condenser, an X-ray tube connected across said condenser, and a discharge circuit for causing an abrupt excitation of the X-ray tube, the said discharge circuit including a spark gap connected in series with the X-ray tube and the condenser, the said condenser instantaneously discharging across the spark gap and X-ray tube immediatelyT after the charge of the condenser exceeds the break down voltage of the spark gap.

2. An X-ray installation for making short X-ray exposures of rapidly changing objects, comprising a storage condenser, a source of alternating Current, means for charging said condenser from said source over a number of current cycles, a two-electrode X-ray tube connected across said condenser, and a discharge circuit including said X-ray tube for discharging said storage condenser at high current intensity and for causing an abrupt, momentary excitation of the X-ray tube, said discharge circuit including a spark gap connected in series With the X-ray tube and the condenser, the spark gap breaking down only after the condenser has received a charge of critical value.

3. An X-ray installation for making short X-ray exposures, comprising a storage condenser, means for charging said condenser, a discharge circuit for said condenser and including a tivo-electrode X-ray tube having an anode and a cathode and leads therefor, and a spark gap in said circuit and disposed in series relation in one of said anode and cathode leads, the said discharge circuit being adapted for causing an abrupt excitation of the X-ray tube, the said condenser instantaneously discharging immediately after the charge of the condenser exceeds the break down voltage of the spark gap.

4. An X-ray installation for making short X-ray exposures, comprising a storage condenser, means for charging said condenser, an X-ray tube connected across said con- February 1928.

ALBERT BOUWERS. 

